ROOFS IN BARE 55% Al-Zn COATED STEEL - STEEL ROOFINGsteelroofing.com/assets/doc/40yearsoflife.pdf · Projected to give 40+YEARS LIFE without major maintenance ROOFS IN BARE 55% Al-Zn

Projected to give

40+YEARS LIFE without major maintenance

ROOFS IN BARE55% Al-Zn

COATED STEEL

Already 20 years old…

At 25, comfortably outpacing galvanized accessories…

30 years young, and goodfor at least another 10…

North American and European validation

Roof in acid rain environment, USA.

55% Al-ZnTHE MAGIC FORMULA

FOR ROOFS

1994

1999

2004

42603 Brochure q6 11/14/05 8:48 AM Page 1

In North America, it’s generally known as Galvalume®.In Europe, it’s also Aluzinc®. And across the world it may bemarketed under Zincalume®, Zintro-Alum®, Galval® and otherbrand names. But whatever the name, one thing is certain:55% Aluminium-Zinc coated steel is the magic formula for roofs.In bare unpainted form, it outperforms all other metallic-coatedsteels, giving more than twice the life of an ordinary zinc coatingof the same thickness and providing superb cut-edge protectionagainst corrosion.

This comprehensive field inspection report shows that even inlow-pitch standing seam roofs it has a life expectancy of wellover 40 years.

It’s no surprise, then, that the technology is now licensed tomanufacturers in more than 28 countries on six continents, or thatexponential growth has seen more than 40 million tonnes producedin the last ten years. By the end of the decade the cumulative totalis predicted to rise to more than 100 million tonnes.

This report covers surveys of established roofs in unpainted 55% Al-Zn in both the USA and Europe. Roofs examined weremainly in urban, industrial, marine and acid rain environments,and ranged in age from 9 to 30 years. Most had a slope of lessthan 10 degrees (1 degree = 1/4:12).

Galvalume®, Aluzinc®, Zincalume®, Zintro-Alum®, and Galval® are internationally recognized and registered trademarks of BIECInternational Inc. or one of its licensed producers.


FOR ROOFS

2


SUMMARY OF FINDINGS• The superior corrosion resistance of bare (unpainted) 55% Al-Zn metallic coated

steel is established beyond any reasonable doubt. Components and accessoriesin galvanized steel were in most cases suffering from advanced deterioration,while the 55% Al-Zn sheets remained virtually unaffected.

• All the roofs were in good to excellent condition both technically andaesthetically – regardless of age, location and environment. The 55% Al-Zn roofpanels performed outstandingly well in North American regions subject to acidrain and harsh winters.

• Based on the field inspection results, all roofs surveyed are projected togive a life in excess of 40 years (some will achieve their half century)without needing major maintenance.

• Environmental conditions play a vital role in the long-term performance ofunpainted 55% Al-Zn roofs, because a highly corrosive environment depletesthe protective metallic coating. Regulatory changes to reduce emissions ofairborne acidifying pollutants (and hence acid rain) mean that the long-termperformance of 55% Al-Zn is likely to increase yet further.

• The buildings surveyed benefited from the excellent solar reflection of 55% Al-Zn sheets, which exceeds the requirements of the US EnvironmentalProtection Agency’s ENERGY STAR® Cool Roof program.

• In some cases, isolated corrosion incidents were observed. These were generallyattributable to design, detailing, installation or maintenance practices – forexample, where ponding had been allowed to occur. In some cases, localisedhighly corrosive environments near chimneys or roof vents had initiated corrosion.

• Quality of design, installation and maintenance is vital to obtain the full benefitof the exceptional corrosion resistance and long life offered by 55% Al-Zn. Thesurvey and the pictures in this report underline the strong recommendation fordesigners and installers to select ancillary fittings and fasteners in materialscompatible with 55% Al-Zn.

3


00

5

10

15

20

25

30

35

10 20 30 40 50 60 70 80Aluminium Content (wt%)

Tim

e to

Firs

t Rus

t (Ye

ars) Industrial

00

5

10

15

20

25

30

35


Tim

e to

Firs

t Rus

t (Ye

ars) Moderate Marine

00

5

10

15

20

25

30

35


Tim

e to

Firs

t Rus

t (Ye

ars) Rural

00

5

10

15

20

25

30

35


Tim

e to

Firs

t Rus

t (Ye

ars) Severe Marine

LIFE EXPECTANCY OF 55% Al-Zn COATED STEELS IS AT LEAST TWICE

THAT OF HOT DIP GALVANIZEDLong-term evaluations show that 55% Al-Zn sheets will have

a life of >30 to 40+ years, except in severe marine applications,and at least twice the life of galvanized steels

4

Galvanized 55% Al-Zn Coated Steel


ROOFS IN NORTH AMERICA:1

Location: Indianapolis, Indiana, USA

Environment: Industrial, acid rain

Slope: 1 degree

Age: 30 years

The deterioration of the galvanized accessories isobvious, but the 55% Al-Zn sheets are virtually likenew, except for a cosmetic reduction of the surfaceshine through dirt accumulation and naturaloxidation. There has been very little change sincethe 1994 survey: indeed, very little change since theroof was first built – despite the acid rainenvironment of Indianapolis.

5

1994

1999

2004



Location: Medina, Ohio, USA

Environment: Urban, severe acid rain and dew

Slope: 1 degree

Age: 32 years

It’s hard to believe, but this roof is sited in an area with severeacid rain. As can be seen from the 1994 and 2004 pictures, theroof also has to contend with heavy morning dews. Despitethese problems, the 55% Al-Zn sheets continue to perform well.In 1999, our inspectors predicted another 10 years life; five yearslater, the prediction confidently stands at the same figure – givinga life of over 40 years with only routine minor maintenance.

Location: Appleton, Wisconsin, USA

Environment: Industrial (Paper Mill)

Slope: 1 degree

Age: 31 years

Nearby paper mills make this an aggressive environment,but despite being more than 30 years old, the 55% Al-Zncoating remains intact and continues to protect the roofsheets from corrosion. This roof looks set to last another 10 years without major maintenance.

6

1994

1999 2004

1994


Location: Appleton, Wisconsin,USA

Environment: Industrial

Slope: 1 degree

Age: 30 years

The main picture confirms the goodcondition of this roof, technically andaesthetically. Picture A demonstratesthat the roof has to accommodate anumber of ancillary structures, someshowing advanced deterioration.Picture B shows that there is onlyminimal damage around fasteningsand at the drip edge.

A B

7

1999 2004




Environment: Urban

Slope: 1 degree

Age: 30 years

Correct specification of fasteners is important to ensuremaximum roof life.



Slope: 5 degrees

Age: 30 years

Dirt has affected thecosmetic appearance ofthis roof after 30 years,but there is no damage to the coating whichcontinues to perform well.

Location: Omaha, Nebraska, USA

Environment: Urban

Slope: 1 degree

Age: 29 years

No problems at the drip edge after nearly 30 years.

8



Environment: Urban

Slope: 1 degree

Age: 30 years

Again, the drip edge is clean andcorrosion-free after 30 years’service. The 55% Al-Zn roof sheetscontinue to perform, althoughaccessories in galvanized steeldisplay significant red rust.

Cleaning has affected the appearance of the 55% Al-Zn sheets,but the drip edge and around the fastenings show no materialdamage after a life of 30 years.

Location: New Orleans, Louisiana, USA


Slope: 1 degree

Age: 26 years

This roof has to cope with rainwater run-off from the extensionon the right. Although the design is not ideal, the 55% Al-Zncoating is performing well.

Location: Fond du Lac, Wisconsin, USA

Environment: Urban

Slope: 2 degrees

Age: 30 years

9


55% Al-Zn COMPARED WITH HOT DIP GALVAOutperforms and outlasts ordinary galvaniz



Slope: 1 degree

Age: 30 years

The galvanized hanger is at an advanced stage of rusting, butthe 55% Al-Zn sheets are in excellent condition.

Location: Bremen, Germany

Environment: Urban

Slope: <5 degrees

Age: 23 years

The performance of 55% Al-Zn on this 23-year-old roof is instark contrast with the deterioration of the hot dip galvanizedsteel roof vent.

Location: Vecoux, France

Environment: Rural

Slope: 20 degrees

Age: 17 years

The post-painted (field-painted) hot dip galvanized roof sectionis in poor condition, and even perforated at a few points. The55% Al-Zn section, though dirty, is in good condition – apartfrom localized corrosion due to pollution from the roof stack.

10


P GALVANIZED IN THE ROOF ENVIRONMENTary galvanized steels, painted or unpainted.

Location: Cumbria, UK

Environment: Rural

Slope: 22 degrees

Age: 18 years

Location: Cambridgeshire, UK (left) and Indiana, USA (right)

Environment: Industrial (UK) and industrial acid rain (USA)

Slope: <5 degrees (UK) and 2 degrees (USA)

Age: 22 years (UK) and 25 years (USA)

Terminal rusting is clear on the galvanized roof vents in both these applications, but the roofing sheets in 55% Al-Zn remain inexcellent condition, despite harsh environments.

11

The 18-year-old 55% Al-Zn roof contrasts with galvanized panelson the right, which had begun to show rust after only 6 years.

The picture clearly shows how the 55% Al-Zn coating sacrificesitself to protect the fasteners.



Slope: 5 degrees

Age: 30 years


Location: Rotterdam,The Netherlands

Environment: Heavy industrial/light marine

Slope: 7 degrees

Age: 18 years

Chemical operations immediately adjacent to acement factory, and the sea a couple of milesaway… a particularly punishing environment.Yet after 18 years the roof in 55% Al-Zn looksas good as new.

ROOFS IN EUROPE

Location: Flemalle, Belgium

Environment: Heavy industrial

Slope: 10 degrees

Age: 26 years

Installed in 1977, the 55% Al-Zn steel roof in the centre ofthe main picture is very dirty, but despite 26 years in ahighly aggressive environment it is still in good condition.A section of the 55% Al-Zn roof abuts on to another profiledsection in pre-painted hot dip galvanized steel, and is alsobordered by unpainted hot-dip galvanized. If ever a picturewere worth a thousand words, this is it: the superiorperformance of 55% Al-Zn is obvious.The drip edge of this roof shows how the 55% Al-Zn coatingcontinues to restrict the spread of red rust.

12


Location: Cumbria, UK

Environment: Rural

Slope: Curved section

Age: 18 years

Not surprisingly, the rural environment of this UK factory has helped the 55% Al-Zn roof sheets to achieve outstanding performance. Even on apotentially troublesome curved section, 55% Al-Zn is still performing well – onlya slight black staining has occurred since the picture on the left was taken in1990. The picture on the right was taken 12 years later.

Location: Chambéry, France

Environment: Urban

Slope: 7 degrees

Age: 22 years

The mountains form a suitably rugged backdrop for this roof,still in excellent condition after 18 years – although a fewseams showed some rusting caused by installation damage.

Location: Falun, Sweden

Environment: Urban

Slope <5 degrees

Age: 15 years

Despite ponding problems where the panels sagged betweenpurlins, this low-slope roof is still in good condition, and predictedto give at least another 15 years’ service.

13

1990 2002


A superior long-life roof system requires not only the rightsheet material, but also good design, installation andmaintenance practices. Both the North American and theEuropean roof surveys confirm the strong performance of bare,unpainted 55% Al-Zn sheets – but at the same time, theyemphasise that maximising life depends upon “best practice”throughout the project.For example, areas around various types of roof-mountedequipment and stacks are often dirty and rust-stained. Goodmaintenance and the use of corrosion-resistant materials tosupport roof-mounted equipment would minimise this.

KEY DESIGN AND INSTALLATION FACTORSSome of the installations surveyed revealed combinationsof galvanized steel, 55% Al-Zn, aluminium, paintedgalvanized and lead being used for curbs, flashings androof accessories. Designers and installers should be carefulto select only those materials that are most compatiblewith the 55% Al-Zn coating, and should be discouragedfrom using shorter-life galvanized steel parts on a long-life 55% Al-Zn roof system. If corrosive vapour is beingdischarged from a roof stack, it may be necessary to post-apply protective coatings to the roof panels in the adjacentaffected area.

Location: Omaha, Nebraska, USA

Environment: Urban

Slope: 1 degree

Age: 29 years

Ponding problem. Sagging of the panels has resulted inponding, and the consequent rust stain is not only unsightly butcan lead to premature corrosion if the ponding issue is notaddressed.


Environment: Urban

Slope: 14 degrees

Age: 18 years

Careless routine maintenance. Here a storm filter wasplugged by debris, due to lack of regular maintenance. Pondingresulted, and corrosive agents released by the bitumen usedto seal roof laps had caused red rust. A neutral cure sealantshould have been used.


Environment: Urban

Slope: 6 degrees

Age: 15 years

Poor installation practice. Iron debris left on the roof hasrusted and stained the roof, although both fastener and sheetare in good condition. Good installation practice and post-installation clean-up would have avoided this. Although there isno accelerated corrosion in this case, the rust stain creates anundesirable cosmetic appearance.

14


Location: Münster, Germany

Environment: Urban

Slope: <5 degrees

Age: 21 years

Poor installation and maintenance practice. How not to doit. The left hand picture shows how the careless use of asphaltas a patch has accelerated corrosion near the drip edge. In theright hand picture, a spare piece of metal flashing was left lyingon the surface of the roof, trapping moisture and debris andleading to accelerated corrosion.

Location: Tyresö, Sweden

Environment: Urban/light marine

Slope: 5 degrees

Age: 20 years

Poor material choice for adjacent chimneys. In the lefthand picture, the use of weathering steel for the chimney in thebackground has caused minor pitting corrosion to the 55% Al-Zn roof after 20 years; copper ions from the chimneymaterial, swept down by rain, will continue to attack anddamage the roof. On the right, the weathering steel chimneyshave caused some corrosion, but there is so far no perforationof the coating. These problems could have been avoided if therecommended design parameters had been observed.

Location: Le Thillot, France

Environment: Urban

Slope: 10 degrees

Age: 10 years

15



FOR ROOFSThe field inspection surveys covered in this paper were carried out in 2002and 2003 (Europe) and 2004 (North America). Both surveys predict a lifeexpectancy of 40+ years for roofs in 55% Al-Zn metallic coated steel. Thissteel is marketed in North America and Europe mainly under the brand namesGalvalume®, Aluzinc®, Zincalume®, Zintro-Alum®, and Galval®.

� The inspections were made by experienced engineers from BIEC InternationalInc, the worldwide licensor of the 55% Al-Zn coated steel technology, andfrom manufacturing licensees in North America and Europe.

� The roofs inspected used 55% Al-Zn steel with a nominal coating thicknessof 20-25 µm and a nominal coating weight of 150 g/m2.

� The inspectors noted age, location, slope and overall appearance of eachroof, along with a general assessment of the environmental conditions. Theassistance and support of the Butler Manufacturing Co. is acknowledged.

� The relative performance of other materials used in such rooftop equipmentand fittings as roof stacks, fasteners and gutter hangers was also recorded.

� Where necessary, mild abrasive pads were used to remove dirt and stains,so that the extent of corrosion could be accurately assessed. Differentlevels of surface contamination and oxidation meant that some of the roofsinspected were dirtier and not as bright as others.

� The results and predictions described in this paper are the educated opinionsof professionals with extensive experience in evaluating material performance.The results and predictions are neither guaranteed nor warranted.

55% Al-Zn Coated Sheet Producers of North America and Europe

For more information and details of manufacturers and sales agencies,visit www.steelroofing.com or www.roofsteel.com

This paper is produced by the ZAC Association,1111 Main Street, Suite 545, Vancouver, WA 98660, USA. July 2005.


Documents

ROOFS IN BARE 55% Al-Zn COATED STEEL - STEEL ROOFINGsteelroofing.com/assets/doc/40yearsoflife.pdf · Projected to give 40+YEARS LIFE without major maintenance ROOFS IN BARE 55% Al-Zn